WEDNESDAY, Aug. 4 (HealthDay News) -- The more weight women pack on during pregnancy, the heavier their babies are likely to be, new research confirms.

And excessive birth weight appears to be associated with being overweight in adulthood, raising the risk of weight-associated diseases, the researchers report in the Aug. 4 issue of The Lancet.

"Because high birth weight predicts BMI (Body Mass Index) later in life, these findings suggest that excessive weight gain during pregnancy could raise the long-term risk of obesity-related disease in offspring," co-authors Dr. David S. Ludwig of Children's Hospital in Boston and Dr. Janet Currie of Columbia University in New York City said in a journal news release.

"High birth weight might also increase risk of other diseases later in life, including asthma, atopy, and cancer," they added.

The researchers tracked the weight gain of both the pregnant woman and her baby in a study that included more than a half-million mothers who had had more than one child, one at a time. This allowed the research team to exclude genetics as the root cause of any maternal-offspring weight connection.

The researchers looked at data from U.S. state-based birth registries, including all known normal-term births -- totaling more than 1,164,000 babies -- in Michigan and New Jersey between 1989 and 2003.

Ludwig and Currie found that women who put on more than 24 kilograms (53 pounds) during pregnancy were more than two times as likely to have a child that weighed at least 4 kg (8.8 pounds) at birth, as compared with women who packed on just 8 to 10 kg (18 to 22 pounds) while pregnant.

In fact, the connection between maternal gain and birth weight appeared to be "consistent," the authors noted, with every kilogram gained by the mother translating into an additional 7.35 grams (2 ounces) in baby weight.

"As more and more Americans struggle with obesity, the role of early prevention is key [and] early prevention may also extend to the development of the fetus," said Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, in a statement. "New population studies show that weight gain in pregnancy impacts birth weight, independent of the genetic factors," she noted.

"More than ever, pregnant women should try to start pregnancies with healthy eating and exercise habits," Wu said.

In a commentary accompanying the journal article, Dr. Neal Halfon and Dr. Michael C. Lu from the Center for Healthier Children, Families and Communities at the University of California, Los Angeles, said that "research is urgently needed into how to help women of reproductive age attain and maintain a healthy weight before and during pregnancy."

"With a growing focus on pre-conceptional health, there is an opportunity to develop effective interventions to help women conceive at a healthier weight," they added, according to the news release.

More information

For more on weight gain during pregnancy, visit the March of Dimes.